- Messages
- 20,561
- Reaction score
- 14,946
- # of dives
- I'm a Fish!
Brian, not true about the color. Some are brown, some are green, some are black. All depends on your supplier and what color they choose....
Nitrox and orings?
- Thread starter Octopusprime
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
I would have to partially disagree with you on this. I do PP fills and I would not fill unless I know that the cylinder, and valve are O2 clean and also not only that all the O rings in, neck, valve stem and face be oxygen compatible, but that the valve seat is an O2 rated seat as well and not nylon 66 (this is very important as its the throttling point). It is not just a matter of making sure the neck O ring and yoke O ring, and as you state, the valve O2 clean, but all components appropriate from tank to fill whip. Only in this way can I as a filler be assured I (hopefully) will not get hurt. If the fill is via a bank or via a membrane machine its not as higher risk so Nx clean tanks are acceptable over Oxygen clean tanks.
For the regulators, secondary regulators are not so critical as you say as the pressures are not as high (although I O2 clean all my regulators on principle), however the 1st stage regulator should be cleaned as well and have fitted appropriate O rings and seats if high oxygen levels are used, however that's an end user problem and not mine if not my regulators. I explain to anyone who I suspect is not familiar with the issues of high O2 risks, but if a tech diver wants an O2 fill and they clearly are certified for 100% Nx, its really not up to me to baby sit them with their gear. For Nx to 40% normally rated regs that quote to 40% are fine (and I think personally in all reality any reg would be fine to 40% Nx)
As an O2 Partial Pressure filler (for me) your cylinder/valve assembly is the critical bit and has to be O2 cleaned and I ask if it has had normal air fills, if so I wont fill it. Whilst this is no guarantee that the cylinder is not contaminated with oil from a bad (supposedly clean) fill, I have at least asked to try and ensure my safety. For myself ALL my air is O2 quality and double filtered whether filling for Nx or just air. Because I can do it cheaply, I O2 clean all my tanks, valves, regulators (1st and second stage), as well as hoses etc. Thus I can use any reg set on any tank or use any tank for any purpose. I do NOT get fills from anyone else so as to ensure my tanks are not contaminated.
I respect the dangers of Oxygen fires and have no wish to experience one in my lifetime. A desire for others to take on risks does not constitute a need or desire for me to.
In Australia we have Nx clean and also Oxygen clean stickers, and while it has never been explained to me the difference, I suspect its only in the valve components that are different, and that the tank is tumbled and both valve and tank cleaned by the same process regardless of the desired end result. I would expect a standard valve kit with Nitrile O ring and Nylon 66 seat when Nx clean to 40%. For 100% oxygen clean, Viton O rings and PCTFE & Carbon Fibre valve seat, however in saying that, why not just get a cylinder/valve O2 cleaned and be done with it as the costs are about the same anyway. Both require a tank and valve clean and a kit.
In Oz we do hydro every year so we have to clean the cylinder after hydro regardless, so we don't get the relief of doing a VIP only and no clean between hydro tests per other countries standards.
---------- Post added May 3rd, 2015 at 12:31 AM ----------
Totally correct. Whilst colour may be an indication of material, it cannot be relied upon. Chinese manufacturers (as perhaps other countries too) do make nitrile O rings in all sorts of pretty colours. Whilst colour coding was probably brought in by something like the airline maintenance section to distinguish between material, it has been so basterdised that one cannot rely on it as an absolute.
---------- Post added May 3rd, 2015 at 12:33 AM ----------
As a side issue, its easy to tell if a component is Teflon, put a flame to it, if its Teflon it will go clear. If its nylon it will burn. (Thanks Steve Burton ASSETT).
Last edited:
- Messages
- 20,561
- Reaction score
- 14,946
- # of dives
- I'm a Fish!
you can't control the fill whip, so that's out
Valve being O2 clean, would imply all of the O-rings are O2 compatible as would the seat ideally. I do o2 clean all of my bottles and first stages out of habit, but as far as O-rings a user might see, the neck O-ring and yoke o-ring are about it. The others inside the valve aren't replaced at VIP time unless the valve is going in for a rebuild.
Valve being O2 clean, would imply all of the O-rings are O2 compatible as would the seat ideally. I do o2 clean all of my bottles and first stages out of habit, but as far as O-rings a user might see, the neck O-ring and yoke o-ring are about it. The others inside the valve aren't replaced at VIP time unless the valve is going in for a rebuild.
From Scuba Doctor website;
Does a cylinder need to be O2 clean in order to receive a Nitrox fill?
Well it depends on if the dive shop doing the filling will be partial pressure blending or not. When a dive shop partial pressure blends Nitrox they add pure Oxygen to the tank first and then top off with air to end up with the desired Nitrox mix. Because pure Oxygen is being used to fill the cylinder initially, the tank and valve must be O2 cleaned and filled with Oxygen compatible air. Oxygen compatible air has been through extra filtration to ensure fewer oils and hydrocarbons as compared to standard air and avoids contaminating the tank and valve. (At The Scuba Doctor ALL of the air we use to fill all cylinders is Oxygen compatible.)
If the dive shop has Nitrox in banks, or uses a compressor with either a membrane system or Nitrox mixing stick to create the Nitrox, then the cylinder being filled does not need to be O2 clean to be filled with Nitrox up to 40%. (That is, the standard practice is to apply what is known as the 40 per cent rule.) In this case the shop will be decanting Nitrox which is already mixed at a fraction of Oxygen (FO2) less than 40% into the tank. More dive shops are beginning to bank Nitrox and have it ready to decant into customers cylinders. Some dive shops keep more Nitrox banked than they do air. Using this method the cylinder and valve never see more than 40% Oxygen and as a result they do not need to be Oxygen cleaned. Cleaning is not required as long as the tank and valve only ever "sees" Nitrox below 40%. At The Scuba Doctor we use partial pressure blending for Nitrox and Trimix fills, so your cylinders and valves need to be O2 clean when getting these fills because they will see 100% Oxygen.
[h=2]What if I want a Nitrox fill over 40%?[/h]This question is asked because many people in the dive industry simply refer to and follow the 40 per cent rule.
The 40 Per Cent Rule
In essence, the 40 Per Cent Rule states that, "If a regulator, cylinder or valve will not be exposed to gas mixtures with an FO2 greater than 40 percent, at pressures greater than regulator intermediate pressure, they need not be O2 clean or service rated." The 40 Percent Rule is widely accepted by divers, dive shops, dive operators and government agencies. Any gas over EAN 40 is treated as Oxygen in terms of handling procedures and the cleaning requirements for cylinders and valves.
So if you require a Nitrox fill over 40%, most dive centres will require you to have an O2 clean cylinder and valve.
Nevertheless, some manufacturers specify that any regulators, cylinders or valves exposed to gas mixtures other than air be O2 clean and service rated. It's not a bad idea to ensure that any cylinder designated for Nitrox use be kept O2 clean and service rated as well, regardless of whether it will be filled using partial-pressure blending or not.
Based in the info above, both valve and tank must be oxygen cleaned if being filled by partial pressure method (for those not familiar with this method, pure oxygen is added to the cylinder and then air/nitrox is used to top up the cylinder to full pressure. Thus at the time oxygen is added to the cylinder, both the valve and cylinder are exposed to Pure oxygen and all the associated risks).
Does a cylinder need to be O2 clean in order to receive a Nitrox fill?
Well it depends on if the dive shop doing the filling will be partial pressure blending or not. When a dive shop partial pressure blends Nitrox they add pure Oxygen to the tank first and then top off with air to end up with the desired Nitrox mix. Because pure Oxygen is being used to fill the cylinder initially, the tank and valve must be O2 cleaned and filled with Oxygen compatible air. Oxygen compatible air has been through extra filtration to ensure fewer oils and hydrocarbons as compared to standard air and avoids contaminating the tank and valve. (At The Scuba Doctor ALL of the air we use to fill all cylinders is Oxygen compatible.)
If the dive shop has Nitrox in banks, or uses a compressor with either a membrane system or Nitrox mixing stick to create the Nitrox, then the cylinder being filled does not need to be O2 clean to be filled with Nitrox up to 40%. (That is, the standard practice is to apply what is known as the 40 per cent rule.) In this case the shop will be decanting Nitrox which is already mixed at a fraction of Oxygen (FO2) less than 40% into the tank. More dive shops are beginning to bank Nitrox and have it ready to decant into customers cylinders. Some dive shops keep more Nitrox banked than they do air. Using this method the cylinder and valve never see more than 40% Oxygen and as a result they do not need to be Oxygen cleaned. Cleaning is not required as long as the tank and valve only ever "sees" Nitrox below 40%. At The Scuba Doctor we use partial pressure blending for Nitrox and Trimix fills, so your cylinders and valves need to be O2 clean when getting these fills because they will see 100% Oxygen.
[h=2]What if I want a Nitrox fill over 40%?[/h]This question is asked because many people in the dive industry simply refer to and follow the 40 per cent rule.
The 40 Per Cent Rule
In essence, the 40 Per Cent Rule states that, "If a regulator, cylinder or valve will not be exposed to gas mixtures with an FO2 greater than 40 percent, at pressures greater than regulator intermediate pressure, they need not be O2 clean or service rated." The 40 Percent Rule is widely accepted by divers, dive shops, dive operators and government agencies. Any gas over EAN 40 is treated as Oxygen in terms of handling procedures and the cleaning requirements for cylinders and valves.
So if you require a Nitrox fill over 40%, most dive centres will require you to have an O2 clean cylinder and valve.
Nevertheless, some manufacturers specify that any regulators, cylinders or valves exposed to gas mixtures other than air be O2 clean and service rated. It's not a bad idea to ensure that any cylinder designated for Nitrox use be kept O2 clean and service rated as well, regardless of whether it will be filled using partial-pressure blending or not.
Based in the info above, both valve and tank must be oxygen cleaned if being filled by partial pressure method (for those not familiar with this method, pure oxygen is added to the cylinder and then air/nitrox is used to top up the cylinder to full pressure. Thus at the time oxygen is added to the cylinder, both the valve and cylinder are exposed to Pure oxygen and all the associated risks).
chrisch
Contributor
If you look under elastomers on this (nothing to do with diving) chart you can see Viton is not considered O2 compatible.
Make of that what you like. Personally I do not use Viton. I think the diving industry has been hoodwinked into this. I am not a chemist or an engineer so if you any of are and you know better please post up and tell us all the truth. I have never seen an issue with standard O rings in 20 years diving.
Learn More About Materials Compatibility
Make of that what you like. Personally I do not use Viton. I think the diving industry has been hoodwinked into this. I am not a chemist or an engineer so if you any of are and you know better please post up and tell us all the truth. I have never seen an issue with standard O rings in 20 years diving.
Learn More About Materials Compatibility
Nope not a chemist, my specialty is Coal Fired Power Stations. I can only go by what I read.
I agree the list shows Viton is not suitable, however there are a lot of postings that say it is. This is like the climate warming argument, experts on both sides.
Seal O-ring selection
O-RING SELECTION M-O
And a list that says Viton is fine with oxygen.
So we now have conflicting experts, isn't that just typical and us laypeople have to decide.
Bad Request
Another that says selected Viton is fine
Last edited:
cool_hardware52
Contributor
Oring? Really? How about that *HUGE* chunk of fuel, aka the Nylon valve seat, in essentially *every* scuba cylinder valve?
Any gas being pumped into the scuba tank impinges directly on the face of this valve seat.
Kinda makes the choice of Oring material seem less vital.
Me? If I have viton I'll use them, if I don't Buna doesn't give me much heartburn.
Whatever I use will be O2 clean….
Tobin
Any gas being pumped into the scuba tank impinges directly on the face of this valve seat.
Kinda makes the choice of Oring material seem less vital.
Me? If I have viton I'll use them, if I don't Buna doesn't give me much heartburn.
Whatever I use will be O2 clean….
Tobin
From the TDI site;
If you own tanks and intend to use them for Nitrox diving (and you should!) there are a couple of things you need to do before filling them with your personal mix.
The Blending Method Counts: SDI dive centers, resorts, and live aboards employ a variety of methods to create Nitrox, including partial-pressure blending in dive cylinders and storage bottles, continuous-blending systems and separation membranes.
Sport divers don’t need to understand the particulars of most of these methods. They do need to be aware, however, that the first of these methods — partial-pressure blending in the end users’ cylinders — exposes both cylinders and valves to oxygen concentrations in excess of 40 percent, at pressures far greater than regulator intermediate pressure. Thus, these cylinders and valves must be oxygen clean and oxygen service rated, to reduce the risk of fire or explosion.
Whether or not to O2 clean other equipment items is dictated by a hierarchy of practices.
The 40 Percent Rule is widely accepted by divers, dive operators and government agencies. Nevertheless, some manufacturers specify that any regulators, cylinders or valves exposed to gas mixtures other than air be O2 clean and service rated. It’s not a bad idea to ensure that any cylinder designated for Nitrox use be kept O2 clean and service rated as well, regardless of whether it will be filled using partial-pressure blending or not.
[h=2]Oxygen Compatible Air[/h]It is important to understand that it is not merely sufficient to have those equipment items that require it O2 cleaned and prepared for Nitrox use; you must also maintain the O2 service rating by exposing these items only to gas mixtures created using oxygen-compatible air.
[h=2]Tank Marking and Identification[/h]Any time you fill a tank with Nitrox, it must be identified as such. This will help to prevent accidents in the event that someone uses a tank filled with Nitrox without taking the proper precautions. The industry standard for tanks filled with Nitrox is to mark the tank with both a tank wrap, as well as to identify the mixture with a label or tag.
A Nitrox tank wrap is an adhesive decal, generally 10-13 cm/4-5 in in width, that is designed to completely encircle the diameter of the tank. The tape is usually printed in yellow with the word Enriched Air and/or Nitrox printed continuously on it in bold green letters. This tape makes it quick and easy to spot a Nitrox bottle in a group of tanks.
It is important to note that, although the industry standard is described and pictured here, some countries require different looking labels by law. Consult a local SDI dive center to discover the local laws require prior to diving.
Any tank used for Nitrox diving must also have a tag or label attached to it where the exact Nitrox mixture used in the tank (FO2) and its MOD can be read. Some shops use plastic tags that can be written on and reused, some use labels stuck to the tank itself, others use duct tape stuck to the cylinder neck. It doesn’t matter which style of marking device is used, as long as the information is instantly available on the tank
---------- Post added May 3rd, 2015 at 02:06 AM ----------
Tobin;
I do believe this bit in my previous post covers your concern re the valve seat;
For 100% oxygen clean, Viton O rings and PCTFE & Carbon Fibre valve seat
Nylon 66 for normal air or potentially Nx to 40%, and from 41% to 100% PCTFE/Carbon Fibre
If you own tanks and intend to use them for Nitrox diving (and you should!) there are a couple of things you need to do before filling them with your personal mix.
The Blending Method Counts: SDI dive centers, resorts, and live aboards employ a variety of methods to create Nitrox, including partial-pressure blending in dive cylinders and storage bottles, continuous-blending systems and separation membranes.
Sport divers don’t need to understand the particulars of most of these methods. They do need to be aware, however, that the first of these methods — partial-pressure blending in the end users’ cylinders — exposes both cylinders and valves to oxygen concentrations in excess of 40 percent, at pressures far greater than regulator intermediate pressure. Thus, these cylinders and valves must be oxygen clean and oxygen service rated, to reduce the risk of fire or explosion.
Whether or not to O2 clean other equipment items is dictated by a hierarchy of practices.
- Local laws, regulations and standards of practice always take precedence over any less-strict requirements.
- Manufacturer’s specifications also take precedence over any less-strict requirements, as dive operators cannot defend a decision based on the fact they presume to “know better” than the engineers who designed a particular piece of equipment.
- Absent the precedence of either of these two factors, the standard of practice is to apply what is known as the 40 Percent Rule.
The 40 Percent Rule is widely accepted by divers, dive operators and government agencies. Nevertheless, some manufacturers specify that any regulators, cylinders or valves exposed to gas mixtures other than air be O2 clean and service rated. It’s not a bad idea to ensure that any cylinder designated for Nitrox use be kept O2 clean and service rated as well, regardless of whether it will be filled using partial-pressure blending or not.
[h=2]Oxygen Compatible Air[/h]It is important to understand that it is not merely sufficient to have those equipment items that require it O2 cleaned and prepared for Nitrox use; you must also maintain the O2 service rating by exposing these items only to gas mixtures created using oxygen-compatible air.
- Standard scuba air — although very clean and dry — still contains trace amounts of hydrocarbons and other contaminants. If allowed to collect on the internal surfaces of cylinders, regulators and valves, these create a risk of fire and/or explosion — a risk that O2 cleaning will eliminate.
- Oxygen-compatible air, on the other hand, is virtually free of hydrocarbons and contaminants. By making certain that the internal surfaces of cylinders, regulators and valves only come in contact with oxygen-compatible air, or gas mixtures created using oxygen-compatible air, you effectively eliminate the risk of fire or explosion, and maintain your equipment’s O2 service rating.
- Only allow this equipment to come in contact with oxygen-compatible air or gas mixtures, or…
- …if the equipment does come in contact with standard scuba air, to remove any markings that indicate it is O2 clean, and not represent to dive operators that any such cylinders are suitable to be filled with Nitrox through in-cylinder partial-pressure blending.
[h=2]Tank Marking and Identification[/h]Any time you fill a tank with Nitrox, it must be identified as such. This will help to prevent accidents in the event that someone uses a tank filled with Nitrox without taking the proper precautions. The industry standard for tanks filled with Nitrox is to mark the tank with both a tank wrap, as well as to identify the mixture with a label or tag.
A Nitrox tank wrap is an adhesive decal, generally 10-13 cm/4-5 in in width, that is designed to completely encircle the diameter of the tank. The tape is usually printed in yellow with the word Enriched Air and/or Nitrox printed continuously on it in bold green letters. This tape makes it quick and easy to spot a Nitrox bottle in a group of tanks.
It is important to note that, although the industry standard is described and pictured here, some countries require different looking labels by law. Consult a local SDI dive center to discover the local laws require prior to diving.
Any tank used for Nitrox diving must also have a tag or label attached to it where the exact Nitrox mixture used in the tank (FO2) and its MOD can be read. Some shops use plastic tags that can be written on and reused, some use labels stuck to the tank itself, others use duct tape stuck to the cylinder neck. It doesn’t matter which style of marking device is used, as long as the information is instantly available on the tank
---------- Post added May 3rd, 2015 at 02:06 AM ----------
Tobin;
I do believe this bit in my previous post covers your concern re the valve seat;
For 100% oxygen clean, Viton O rings and PCTFE & Carbon Fibre valve seat
Nylon 66 for normal air or potentially Nx to 40%, and from 41% to 100% PCTFE/Carbon Fibre
cool_hardware52
Contributor
Cool, if these are actually available.
Some number of years ago I looked into making valve seats from Kel-F. Somewhere around here I still have the samples.
Proved to be a non trivial task, and the Kel-F I sourced was hard enough to wear the brass mating surfaces pretty quickly.
Maybe they have a different blend that seals without distorting the brass.
The issue of course with O2 Compatible sealing components is the stuff that is mailable is typically pretty good "fuel" and the stuff with a High Index is often either really soft (PTFE) and cold flows, or is really hard and doesn't seal very well.
Tobin
The PCTFE/Carbon fibre is, I just ordered some
Similar threads
